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                    SQL常用使用
            
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                    spring security 配置发生错误 Can't configure antMatchers after anyRequest
            
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<h3 id="hashmap"><a name="hashmap" class="anchor-navigation-ex-anchor" href="#hashmap"><i class="fa fa-link" aria-hidden="true"></i></a><strong>HashMap</strong></h3>
<p>&#x200B;    <strong>HashMap</strong>&#x7EBF;&#x7A0B;&#x4E0D;&#x5B89;&#x5168;&#xFF0C;&#x5728;&#x591A;&#x7EBF;&#x7A0B;&#x73AF;&#x5883;&#x4E0B;&#xFF0C;&#x4F7F;&#x7528;HashMap&#x8FDB;&#x884C;put&#x64CD;&#x4F5C;&#x4F1A;&#x5F15;&#x8D77;&#x6B7B;&#x5FAA;&#x73AF;&#xFF0C;&#x5BFC;&#x81F4;CPU&#x5229;&#x7528;&#x7387;&#x63A5;&#x8FD1;100%&#xFF0C;&#x662F;&#x56E0;&#x4E3A;&#x591A;&#x7EBF;&#x7A0B;&#x4F1A;&#x5BFC;&#x81F4;HashMap&#x7684;Entry&#x94FE;&#x8868;&#x5F62;&#x6210;&#x73AF;&#x5F62;&#x6570;&#x636E;&#x7ED3;&#x6784;&#xFF0C;&#x4E00;&#x65E6;&#x5F62;&#x6210;&#x73AF;&#x5F62;&#x6570;&#x636E;&#x7ED3;&#x6784;&#xFF0C;Entry&#x7684;next&#x8282;&#x70B9;&#x6C38;&#x8FDC;&#x4E0D;&#x4E3A;&#x7A7A;&#xFF0C;&#x5C31;&#x4F1A;&#x4EA7;&#x751F;&#x6B7B;&#x5FAA;&#x73AF;&#x83B7;&#x53D6;Entry&#x3002;   </p>
<h3 id="hashtable"><a name="hashtable" class="anchor-navigation-ex-anchor" href="#hashtable"><i class="fa fa-link" aria-hidden="true"></i></a><strong>HashTable</strong></h3>
<p>&#x200B;    <strong>Hashtable</strong>&#x5BB9;&#x5668;&#x4F7F;&#x7528;<strong>synchronized</strong>&#x6765;&#x4FDD;&#x8BC1;&#x7EBF;&#x7A0B;&#x5B89;&#x5168;&#xFF0C;&#x6240;&#x4EE5;&#x5728;&#x7EBF;&#x7A0B;&#x7ADE;&#x4E89;&#x6FC0;&#x70C8;&#x7684;&#x73AF;&#x5883;&#x4E0B;&#x6548;&#x7387;&#x975E;&#x5E38;&#x4F4E;&#x4E0B;&#x3002;&#x56E0;&#x4E3A;&#x5F53;&#x4E00;&#x4E2A;&#x7EBF;&#x7A0B;&#x8BBF;&#x95EE;HashTable&#x7684;&#x540C;&#x6B65;&#x65B9;&#x6CD5;&#xFF0C;&#x5176;&#x4ED6;&#x7EBF;&#x7A0B;&#x4E5F;&#x8BBF;&#x95EE;HashTable&#x7684;&#x540C;&#x6B65;&#x65B9;&#x6CD5;&#x65F6;&#xFF0C;&#x4F1A;&#x8FDB;&#x5165;&#x963B;&#x585E;&#x6216;&#x8F6E;&#x8BE2;&#x72B6;&#x6001;&#x3002;&#x5982;&#x7EBF;&#x7A0B;A&#x8BBF;&#x95EE;put&#x8FDB;&#x884C;&#x5143;&#x7D20;&#x6DFB;&#x52A0;&#x65F6;&#xFF0C;&#x5176;&#x4ED6;&#x7EBF;&#x7A0B;&#x4E0D;&#x4F46;&#x4E0D;&#x80FD;&#x4F7F;&#x7528;put&#x65B9;&#x6CD5;&#xFF0C;&#x4E5F;&#x4E0D;&#x80FD;&#x4F7F;&#x7528;get&#x65B9;&#x6CD5;&#x83B7;&#x53D6;&#x5143;&#x7D20;&#x3002;   </p>
<table>
<thead>
<tr>
<th style="text-align:center">HashMap/HashTable&#x533A;&#x522B;</th>
<th style="text-align:center">HashMap</th>
<th style="text-align:center">HashTable</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align:center">&#x7EBF;&#x7A0B;&#x5B89;&#x5168;</td>
<td style="text-align:center">&#x975E;&#x7EBF;&#x7A0B;&#x5B89;&#x5168;</td>
<td style="text-align:center">&#x7EBF;&#x7A0B;&#x5B89;&#x5168;</td>
</tr>
<tr>
<td style="text-align:center">NULL&#x503C;</td>
<td style="text-align:center">key&#x548C;value&#x90FD;&#x53EF;&#x4EE5;&#x4E3A;null</td>
<td style="text-align:center">&#x4E0D;&#x5141;&#x8BB8;key&#x4E3A;null</td>
</tr>
<tr>
<td style="text-align:center">&#x7EE7;&#x627F;&#x5173;&#x7CFB;</td>
<td style="text-align:center">&#x7EE7;&#x627F;AbstractMap</td>
<td style="text-align:center">&#x7EE7;&#x627F;Dictionary</td>
</tr>
<tr>
<td style="text-align:center">&#x5BB9;&#x5668;&#x521D;&#x59CB;&#x503C;</td>
<td style="text-align:center">16</td>
<td style="text-align:center">11</td>
</tr>
<tr>
<td style="text-align:center">&#x6269;&#x5BB9;&#x65B9;&#x5F0F;</td>
<td style="text-align:center">capacity*2</td>
<td style="text-align:center">capacity*2+1</td>
</tr>
<tr>
<td style="text-align:center">&#x5E95;&#x5C42;&#x7ED3;&#x6784;</td>
<td style="text-align:center">&#x6570;&#x7EC4;+&#x94FE;&#x8868;</td>
<td style="text-align:center">&#x6570;&#x7EC4;+&#x94FE;&#x8868;</td>
</tr>
<tr>
<td style="text-align:center">&#x54C8;&#x5E0C;&#x7B97;&#x6CD5;</td>
<td style="text-align:center">&#x5BF9;key&#x7684;hashcode&#x8FDB;&#x884C;&#x4E8C;&#x6B21;hash&#xFF0C;&#x4EE5;&#x83B7;&#x53D6;&#x66F4;&#x597D;&#x7684;&#x6563;&#x5217;&#x503C;&#xFF0C;&#x7136;&#x540E;&#x5BF9;&#x6570;&#x7EC4;&#x957F;&#x5EA6;&#x53D6;&#x6A21;</td>
<td style="text-align:center">&#x76F4;&#x63A5;&#x4F7F;&#x7528;key&#x7684;hashcode,&#x7136;&#x540E;&#x5BF9;&#x6570;&#x7EC4;&#x957F;&#x5EA6;&#x53D6;&#x6A21;</td>
</tr>
</tbody>
</table>
<h3 id="concurrenthashmap"><a name="concurrenthashmap" class="anchor-navigation-ex-anchor" href="#concurrenthashmap"><i class="fa fa-link" aria-hidden="true"></i></a><strong>ConcurrentHashMap</strong></h3>
<p>&#x200B;    <strong>ConcurrentHashMap</strong>&#x6240;&#x91C7;&#x7528;&#x7684;&#x662F;<strong>&#x9501;&#x5206;&#x6BB5;&#x6280;&#x672F;</strong>&#xFF1A;&#x9996;&#x5148;&#x5C06;&#x6570;&#x636E;&#x5206;&#x6210;&#x4E00;&#x6BB5;&#x4E00;&#x6BB5;&#x5730;&#x5B58;&#x50A8;&#xFF0C;&#x7136;&#x540E;&#x7ED9;&#x6BCF;&#x4E00;&#x6BB5;&#x6570;&#x636E;&#x914D;&#x4E00;&#x628A;&#x9501;&#xFF0C;&#x5F53;&#x4E00;&#x4E2A;&#x7EBF;&#x7A0B;&#x5360;&#x7528;&#x9501;&#x8BBF;&#x95EE;&#x5176;&#x4E2D;&#x4E00;&#x4E2A;&#x6BB5;&#x6570;&#x636E;&#x7684;&#x65F6;&#x5019;&#xFF0C;&#x5176;&#x4ED6;&#x6BB5;&#x6570;&#x636E;&#x4E5F;&#x80FD;&#x88AB;&#x5176;&#x4ED6;&#x7EBF;&#x7A0B;&#x8BBF;&#x95EE;&#xFF0C;&#x8FD9;&#x6837;&#x53EF;&#x6709;&#x6548;&#x7684;&#x63D0;&#x5347;&#x5E76;&#x53D1;&#x8BBF;&#x95EE;&#x7387;&#x3002;   </p>
<p>&#x200B;    <strong>ConcurrentHashMap</strong>&#x662F;&#x7531;<strong>Segment</strong>&#x6570;&#x7EC4;&#x7ED3;&#x6784;&#x548C;<strong>HashEntry</strong>&#x6570;&#x7EC4;&#x7ED3;&#x6784;&#x7EC4;&#x6210;&#x3002;</p>
<p>&#x200B;    <strong>Segment</strong>&#x662F;&#x4E00;&#x79CD;&#x53EF;&#x91CD;&#x5165;&#x9501;(ReentrantLock),&#x5728;<strong>ConcurrentHashMap</strong>&#x4E2D;&#x626E;&#x6F14;&#x9501;&#x7684;&#x89D2;&#x8272;&#xFF0C;HashEntry&#x5219;&#x7528;&#x4E86;&#x5B58;&#x50A8;&#x952E;&#x503C;&#x5BF9;&#x6570;&#x636E;&#x3002;</p>
<p>&#x200B;    &#x4E00;&#x4E2A;<strong><em>ConcurrentHashMap</em></strong>&#x91CC;&#x5305;&#x542B;&#x4E00;&#x4E2A;Segment&#x6570;&#x7EC4;&#x3002;</p>
<p>&#x200B;    <strong>Segment</strong>&#x7684;&#x7ED3;&#x6784;&#x548C;hashmap&#x7C7B;&#x4F3C;&#xFF0C;&#x662F;&#x4E00;&#x79CD;&#x6570;&#x7EC4;&#x548C;&#x94FE;&#x8868;&#x7ED3;&#x6784;&#x3002;</p>
<p>&#x4E00;&#x4E2A;Segment&#x91CC;&#x5305;&#x542B;&#x4E00;&#x4E2A;HashEntry&#x6570;&#x7EC4;&#xFF0C;&#x6BCF;&#x4E2A;HashEntry&#x662F;&#x4E00;&#x4E2A;&#x94FE;&#x8868;&#x7ED3;&#x6784;&#x7684;&#x5143;&#x7D20;&#xFF0C;&#x6BCF;&#x4E00;&#x4E2A;Segment&#x5B88;&#x62A4;&#x7740;&#x4E00;&#x4E2A;HashEntry&#x6570;&#x7EC4;&#x91CC;&#x7684;&#x5143;&#x7D20;&#xFF0C;&#x5F53;&#x5BF9;HashEntry&#x6570;&#x7EC4;&#x7684;&#x6570;&#x636E;&#x8FDB;&#x884C;&#x4FEE;&#x6539;&#x65F6;&#xFF0C;&#x9996;&#x5148;&#x5FC5;&#x987B;&#x83B7;&#x53D6;&#x5B83;&#x5BF9;&#x5E94;&#x7684;Segment&#x9501;&#x3002;   </p>
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